Phenylacetylene (C₈H₆)

Models of C₈H₆ were made using the best ab initio level of theory, which was double zeta valence, DZV.  This is the best level of theory because it is the highest basis set of calculations run though it for the molecule.

Bond lengths of C₈H₆ were found using the ab initio levels.
See picture about for corresponding atom numbers.

Atom 1	Atom 2	Bond Length 321G	Bond Length Experimental1
1	2	1.072 Å	1.087Å
1	3	1.385Å	1.397Å
1	7	1.382Å	1.393Å
3	4	1.385Å	1.397Å
3	14	1.072Å	1.087Å
4	5	1.382Å	1.393Å
4	13	1.072Å	1.087Å
5	6	1.391Å	1.408Å
5	12	1.071Å	1.074Å
6	7	1.391Å	1.408Å
6	9	1.434Å	1.430Å
7	8	1.071Å	1.087Å
9	10	1.820Å	1.210Å
10	11	1.050Å	1.066Å

As follows is a visual model of the bond angles in phenylacetylene, with the number nearest the angle representing each's measured value.


The bond angles of C₈H₆ at the level of theory, 321G as well as the literature value with reference.  Look to bond length photo for coresponding atom numbers.

Atoms	Bond Angle	Experimental Bond Angle1
6-9-10	178.956	180.000
6-5-12	119.215	120.114
6-7-8	119.662	139.114
9-6-7	119.979	139.740
5-6-7	119.450	119.611
5-4-13	119.808	120.779
7-1-2	119.900	120.256
4-3-1	120.362	119.843
1-7-8	120.091	100.493
3-4-13	120.410	119.821
6-5-4	120.355	119.767
6-7-1	120.247	119.767
9-6-5	120.571	119.611
9-10-11	197.759	180.000
5-4-3	119.777	119.923
7-1-3	119.807	119.923
4-5-12	120.429	120.119
4-3-14	119.705	120.079
1-3-14	119.932	120.179
3-1-2	120.280	119.821

The button C₈H₆POTENTIAL will appear in the box below.


Click below to view the phenylacetylene HOMO orbital.  The HOMO orbital is the highest energy molecular orbital occupied by electrons.   From the model, it can be predicted how a molecule will react.

 
Click below to view the phenylacetylene LUMO obital.  The LUMO orbital is the lowest unoccupied molecular orbital.  From the model, it can be predicted how the molecule will react.



The dipole moment for the C₈H₆ at the 321G basis set as well as the literature value.

321G	Experimental Value1
0.665 Debye	0.656 Debye

Through the ab initio DZV level of theory, the transition energy was found to be 207.802 nm.  The experimental values were found by looking at the UV-Vis Spectrum for phenylacetylene.  The values found do not match the experimental values. 

For more information on phenylacetylene go to the NIST Website.

Reference
(1) U.S. Secretary of Commerce, Computational Chemistry Comparison and Benchmark
DataBase, on behalf of the United States of America, 2010. Website: <http://cccbdb.nist.gov/>